gha/validate-reno: switch to latest node lts

Author: dctrwatson

.github/workflows/validate-renovate.yml

@@ -16,6 +16,6 @@ jobs:
 
       - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
-          node-version: 20
+          node-version: lts/*
 
       - run: npx -p renovate renovate-config-validator renovate.json